1. Field of the Invention
This invention relates to a process for producing a hydroxyfatty acid polyhydric alcohol ester from Sophorolipid which is a fermentation product of Torulopsis bombicola.
2. Description of the Prior Art
It has been reported by J. F. T. Spencer et al [Canadian Journal of Chemistry, 39, 846 (1961)] that a great quantity of Sophorolipid is produced in a fermentation liquid by culturing Torulopsis bombicola.
Sophorolipid is a mixture of the compounds represented by the formulae (I) and (II), ##STR2## EQU I-a: R.sub.1 =R.sub.2 =COCH.sub.3 EQU I-b: R.sub.1 =COCH.sub.3, R.sub.2 =H EQU I-c: R.sub.1 =H, R.sub.2 =COCH.sub.3 EQU I-d: R.sub.1 =R.sub.2 =H EQU II-a: R.sub.1 =R.sub.2 =COCH.sub.3 EQU II-b: R.sub.1 =COCH.sub.3, R.sub.2 =H EQU II-c: R.sub.1 =H, R.sub.2 =COCH.sub.3 EQU II-d: R.sub.1 =R.sub.2 =H
wherein R.sub.3 represents H or CH.sub.3, and R.sub.4 represents a saturated or unsaturated hydrocarbon group having 11 to 15 carbon atoms when R.sub.3 is CH.sub.3.
As is clear from the above formulae, Sophorolipid contains a hydroxyfatty acid having a hydroxy group at the .omega. or .omega.-1 position in its structure, which can not be synthesized without much difficulty. This hydroxyfatty acid can be used as a raw material for a large ring lactone musk possessing a musky perfume which is highly valued. In fact, various attempts have been made to produce the hydroxyfatty acid by synthetic means, and many reports on this problem have been made public. However, these known synthetic methods are industrially unacceptable because of difficult availablity of raw materials, complexity of processes and difficult processing. As a result, such large ring lactone musk is now marketed as an expensive perfume.
If the hydroxyfatty acid for synthesizing the large ring lactone musk can be produced from Sophorolipid such a process is industrially superior because a great deal of Sophorolipid is economically available by a fermentation method.
Deacylation of Sophorolipid has been reported as a process for producing a hydroxyfatty acid using Sophorolipid as a raw material (Japanese Patent Publication No. 45-947). According to this report, the thus obtained hydroxypalmitic acid is lactonized to give a large ring lactone musk which is obtained at a cost as low as 1/20 of that by any conventional synthetic method.
This process contains the steps of producing the hydroxypalmitic acid from Sophorolipid, reacting this acid with glycerine to produce a hydroxyfatty acid ester or hydroxyfatty acid polymer, and obtaining a large ring lactone musk by ester interchange.
This process involves the following complicated steps:
(1) Hydrolyzing Sophorolipid with the use of an acid or alkali. PA1 (2) Extracting hydroxypalmitic acid with an organic solvent. PA1 (3) Separating the aqueous layer containing glucoside. PA1 (4) Concentrating the organic solvent layer. PA1 (5) Fractionally crystallizing the hydroxypalmitic acid by recrystallization of the extract in the organic solvent. PA1 (6) Producing an intermediate for a large ring lactone musk by esterification or polymerization of the hydroxypalmitic acid.
The present inventors have examined a wide variety of processes for producing a large ring lactone musk in order to eliminate the shortcomings of the conventional process and have succeeded in producing a hydroxyfatty acid ester from Sophorolipid for a raw material for use as synthesizing a large ring lactone. Sophorolipid produced by fermentation can be obtained only in a hydrated form by any separating means. Sophorolipid has a viscosity of more than 100,000 cps in its dehydrated form at room temperature and more than 20,000 cps even at 80.degree. C. Therefore, it is nearly impossible to dehydrate Sophorolipid on an industrial basis. Accordingly, the hydrous system is indispensable in order to yield a hydroxyfatty acid from Sophorolipid by hydrolysis. The present inventors have made many studies concerning lowering the viscosity of Sophorolipid in order to obtain dehydrated Sophorolipid and produce a hydroxyfatty acid derivative directly from Sophorolipid. As a result of these studies, they have found that particular polyhydric alcohols possess good miscibility with Sophorolipid and that the viscosity of Sophorolipid is significantly decreased by adding these polyhydric alcohols, which can act as esterifying agents with the hydroxyfatty acid. Based on this finding, the present invention has been accomplished.